J Syst Evol ›› 2018, Vol. 56 ›› Issue (1): 35-47.DOI: 10.1111/jse.12276

• Research Articles • Previous Articles     Next Articles

Towards resolving the evolutionary history of Caucasian pears (Pyrus, Rosaceae)—Phylogenetic relationships, divergence times and leaf trait evolution

Nadja Korotkova1*, Gerald Parolly1, Anahit Khachatryan2, Lusine Ghulikyan3, Harutyun Sargsyan4, Janna Akopian2, Thomas Borsch1,5, and Michael Gruenstaeudl5   

  1. 1Botanischer Garten und Botanisches Museum Berlin, Freie Universität Berlin, Königin-Luise-Strasse 6-8, 14195 Berlin, Germany
    2Armen L. Takhtajan Institute of Botany, National Academy of Sciences of the Republic of Armenia, Yerevan, Armenia
    3L. A. Orbeli Institute of Physiology, National Academy of Sciences of the Republic of Armenia, Yerevan, Armenia
    4Yerevan State University, Yerevan, Armenia
    5Institut für Biologie, Systematische Botanik und Pflanzengeographie, Freie Universität Berlin, 14195 Berlin, Germany
  • Received:2016-09-06 Published:2018-01-12

Abstract: With approximately 25 endemic species, the genus Pyrus (pears) is highly diverse in the Caucasus ecoregion. The majority of Caucasian pears inhabit xerophytic open woodlands or similar habitats, to which they display morphological adaptations, such as narrow leaves. The other species, both Caucasian and non-Caucasian taxa, mainly inhabit mesophytic forests and display broad leaves. Using a representative taxon sampling of Pyrus from the Caucasus, Europe and Asia, we reconstruct phylogenetic relationships in the genus based on multiple plastid regions. We also estimate the divergence times of major clades in Pyrus, reconstruct the evolution of leaf shapes, and discuss the emergence of xeromorphic leaf traits. Our results confirm the monophyly of Pyrus and the existence of two major clades: (a) an E Asian clade with a crown group age of 15.7 (24.02–8.37 95% HPD) My, and (b) a W Eurasian clade that comprises species from Europe, SW Asia and the Caucasus and that displays a slightly younger crown group of 12.38 (19.02–6.41 95% HPD) My. The existing infrageneric classification of Pyrus was found partially incongruent with the inferred phylogenetic trees. Several currently accepted species were not recovered as monophyletic, indicating that current species limits require re-evaluation. Ancestral character state reconstructions revealed several independent transitions from broad- to narrow-shaped leaves in Pyrus, probably via intermediate-shaped leaves.

Key words: Caucasus, Europe, leaf shape, morphological characters, paleogeography, phylogeny, taxonomy